Diisobutylaluminum hydride → (5alpha)-Pregn-2-en-20-ol

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To a solution of 5-α-pregn-2-en-20-one (11) (860 mg, 2.86 mmol) in anhydrous dichloromethane (120 mL) at −78° C. under an argon atmosphere was slowly added DIBAL-H (1.0 M in hexane) (5.72 mL, 5.72 mmol). The solution was stirred at −78° C. over a period of 3 h and successively washed with an aqueous HCl solution (5%) and a Rochelle salt solution. The organic phase was then filtered using a phase separator syringe (Biotage) and evaporated. Purification by FCC (EtOAc/hexanes, 5:95) yielded 672 mg (78%) of title compound 12 as a white solid. 1H NMR (CDCl3) δ: 0.76 (s, 18-CH3 and 19-CH3), 1.13 (d, J=6.1 Hz, 21-CH3), 0.70-2.10 (residual CH and CH2), 3.73 (m, 20-CH), 5.58 (m, 2-CH and 3-CH). 13C NMR (CDCl3) δ; 11.7, 12.5, 20.8, 23.6, 24.4, 25.6, 28.7, 30.3, 31.9, 34.6, 35.4, 39.8, 40.1, 41.4, 42.4, 54.0, 55.9, 58.6, 70.6, 125.8, 126.0. LRMS for C21H33 [MH—H2O]+: 285.2 m/z.

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